1. Field of the Invention
The present invention relates to new compositions in the treatment of mammalian diseases containing an aqueous surfactant in combination with a bactericidal agent or a biological response modifier to effectively enhance the biological activity and/or decrease the undesirable side effects thereof.
2. Description of the Related Art
Infectious diseases are a leading cause of hospitalization and morbidity in human and veterinary medicine. Improved methods of prevention and therapy remain a major unfilled need in medicine. Despite significant progress in infectious disease control due to widespread adoption of aseptic practices and antibiotic treatment, many infectious diseases remain refractory to treatment. In veterinary medicine, for example, clinical bovine mastitis is of serious economic importance and causes annual losses of an estimated $2 billion to dairy farmers in the United States alone, primarily due to discarded milk with antibiotic residues. One of the foremost etiological agents contributing to this loss is Staphylococcus aureus. Intramammary infections caused by S. aureus are usually chronic and subclinical in nature. The current treatment for S. aureus mastitis is antibiotic therapy. The conventional therapy is nevertheless considered undesirable because of its moderate to low efficacy in producing only a 25% to 50% cure rate and because of the typical three to four day milk discard due to antibiotic residues. The ineffectiveness of current antibiotic therapy has been attributed to some antibiotic resistant strains of S. aureus and to the sequestration of S. aureus within the host's cell. For this reason, bovine mastitis provides a valuable in vivo model to study infectious diseases of mammals.
Mucolytic peptides, such as lysostaphin, have been suggested to be efficacious in the treatment of S. aureus infections of humans (Schaffner et al., Yale J. Biol. & Med., 39:230 (1967) and bovine mastitis caused by S. aureus (Sears et al., J. Dairy Science, 71 (Suppl. 1): 244(1988)). Lysostaphin, a gene product of Staphylococcus simulans, exerts a bacteriostatic and bactericidal effect upon S. aureus by enzymatically degrading the polyglycine crosslinks of the cell wall (Browder et al., Res. Comm., 19: 393-400 (1965)). U.S. Pat. No. 3,278,378 describes fermentation methods for producing lysostaphin from culture media of S. staphylolyticus, later renamed S. simulans. Other methods for producing lysostaphin are further described in U.S. Pat. Nos. 3,398,056 and 3,594,284. The gene for lysostaphin has subsequently been cloned and sequenced (Recsei et al., Proc. Natl. Acad. Sci. USA, 84: 1127-1131 (1987)). The recombinant mucolytic bactericidal protein, such as r-lysostaphin, can potentially circumvent problems associated with current antibiotic therapy because of its targeted specificity, low toxicity and possible reduction of biologically active residues. Furthermore, lysostaphin is also active against non-dividing cells, while most antibiotics require actively dividing cells to mediate their effects (Dixon et al., Yale J. Biology and Medicine, 41: 62-68 (1968)). However, in vivo studies by Oldham, et al., J. Dairy Science, 74:4413 (1991), have demonstrated that the therapeutic efficacy of lysostaphin is not equivalent to the commercially available product CEFA-LAK.RTM. (cephapirin sodium, available from Bristol-Meyers, Evansville, Ind.).
Polymorphonuclear neutrophils (PMNs) also play a critical role in the pathophysiology of most bacterial infections. For example, it has been found that greater than 90% of the cells in an infected gland are PMNs (Daley et al., American Journal of Veterinary Research, 52 (3): 474-479 (1991)). PMNs demonstrate 10,000 fold variation in the efficiency of intracellular killing of S. aureus during somatic cell count cycling. PMNs from a gland infected with S. aureus are both quantitatively (total somatic cell count) and qualitatively (intracellular killing and phagocytic ability) different during the course of a cycling infection. Both the quantity and quality of phagocytic cells play a central role in the defense of the host against infections. It is seen that PMN activity (especially phagocytosis and intracellular killing) can be specifically manipulated using recombinant bovine cytokines and other bioresponse modifiers in the bovine mammary gland to elicit mastitis cures.
A number of cytokines stimulate the growth and differentiation of hematopoietic and other somatic cells. For example, a cytokine such as GM-CSF is able to increase the development of granulocytes and macrophages. Lymphokines such as IL-2 are found to be secreted by T cells when stimulated by antigenic substances and IL-2 receptors have been described to be expressed by T cells, B cells, macrophages and specialized epithelium. Methods for preparing cytokines are well described in the literature (see, for example, Cerretti et al., Cloning sequence and expression of bovine interleukin-2, P.N.A.S., 83:3223-3227 (1986); Maliszewski et al., Cloning, sequence and expression of bovine interleukin 1.sub.a and interleukin 1.sub.b complementary DNAs, Molecular Immunology, 25:429-435 (1988); Maliszewski et al., Bovine GM-CSF: Molecular cloning and biological activity of the recombinant protein, Molecular Immunol., 25: 843-50 (1988); March et. al., Cloning, sequence and expression of two distinct human interleukin-1 complementary DNAs, Nature, 315:641-648 (1985)). Many cytokine genes have been cloned, expressed and characterized making possible the employment of recombinantly derived proteins in the therapy of a variety of hematopoietic and immune diseases (Cantrell et al., Proc. Natl. Acad. Sci. USA, 82:6250-6254 (1985)). Many of these immunomodulators, however, cause certain undesirable side effects which severely limit their practical usefulness (Winkelhake et al., Human recombinant interleukin-2 as an experimental therapeutic, Pharmacological Rev., 42:1 (1990); Taguchi, Clinical effects of interferon on malignancies, Japan J. Cancer Chemo., 11:194 (1984); Dinarello et al., Multiple biological activities of human recombinant interleukin-1, J. Clin. Invest., 77:1734 (1986)).
Ideally, the composition useful in infectious disease therapy should be optimized for efficacy, have minimal residues and have minimal toxic effects. Considering the level of efficacy of the currently available commercial preparations for some infectious diseases, new therapeutics which would have improved biological potency with little or no side effects are highly desirable.